How to Build a PC - Choosing a CPU Cooler

By Dustin Sklavos, on October 25, 2013 08:55 AM

The potential silence and performance of your build is governed by a few things. While overclocking performance is always ultimately going to be up to the potential of the CPU you choose and it most definitely can be a lottery (especially with Haswell), you can do a lot to mitigate limitations on overclocking by choosing the right cooler for your CPU. When it comes to overclocking performance, you really only want to be gated by the CPU’s ability to handle high speeds and voltages as opposed to thermal constraints brought on by questionable cooling choices.

As I mentioned before, a case with good thermal performance can be a large part of it, but the bulk of that airflow goes toward feeding the coolers on your graphics card (or cards) and CPU. And while Intel and AMD’s stock coolers aren’t horrible, they’re really only designed to handle their chips at stock clocks. Under sustained load, these coolers are capable of producing a decent amount of noise and their thermal performance is only adequate at best. Choosing a cooler for your CPU will, like the case, help to define the thermal and noise boundaries of your build.

When choosing a cooler, there are three primary factors to consider: the architecture of the CPU you’re using, whether or not you’re going to overclock, and whether noise level is a priority. Note that you can have high overclocking performance and a silent machine if you buy the right cooler and spend time properly tuning your system, and there’s very little more satisfying than being at the helm of a computing beast that barely hums.

In addition to those primary factors, there’s a secondary consideration: form factor. Once you’ve decided what your priorities are, the cooler you choose needs to be able to actually fit the enclosure you’re using.

While we’ve dabbled in air coolers in the past, our focus now is on closed loop liquid cooling. This is a relatively new technology that combines the bulk of the performance of a custom water cooling loop with the ease of installation of a garden variety air cooler. While closed loop coolers, or CLCs, run the risk of leaks or pump failure, these risks are both fairly minute and overstated. Our CLCs use non-conductive coolant, so even if there’s a leak it’s unlikely the leak itself will damage your hardware.

In exchange for these risks, you get tremendous benefits. While air coolers can be very heavy and place tremendous stress on the motherboard, the bulk of a CLC is the radiator, which mounts directly to the case. Only the pump and waterblock mount to the CPU, and these weigh comparatively little. The radiator also tends to be mounted to the back or top of the case, and depending on the orientation of its fans, can draw in fresh air from the outside of the case or direct air from the inside of the case straight through the radiator fins and out of the back. Either way, airflow is focused and directed, while air cooler performance can be subject to the direction of airflow within the enclosure. Finally, key to cooling is being able to dissipate heat from the source across as much surface area as possible, and it’s tough to beat the surface area and density of a radiator. Coolant inside the CLC constantly flows across the interior of the waterblock, pulling heat off of the CPU and moving it into the radiator where it can be dissipated across the fin array and essentially removed by the fans. And while we generally recommend installing our coolers as intakes to maximize CPU cooling performance, they’re still excellent when installed as exhausts, pushing CPU heat out of the case and allowing your graphics cards to breathe.

With all this information in hand, we can go about choosing the right cooler for your system. If you’re not overclocking and just want to focus on running a quiet system, something basic like our H60 will certainly get the job done. Its 120mm radiator is compatible with all of our cases, and the single PWM-controlled fan will only ever spin up when it needs to.

If you’re overclocking, things get a little bit more complicated. Under those circumstances it’s hard to say “there’s too much cooling.” Certainly you can wind up with excess thermal capacity in your cooling system, but that typically just translates into the fans running at lower speeds and thus giving you a quieter computing experience. At this point selecting a cooler is also going to be governed by which coolers your case can support. All of the product pages for our cases will tell you which sizes of CLCs they support, but typically the majority of cases support a 120mm CLC like our H75 or H80i in the rear exhaust fan mount. Cases with 140mm exhaust fans will typically support a 140mm CLC like our H90 as well, and the lion’s share of cases being launched today will have support for a 240mm CLC like our H100i in the top at a minimum. If you need maximum cooling potential, there’s the H110, but it requires space for a 280mm radiator in the top of the case.

From here, you do want to keep in mind the needs of your specific processor. An Ivy Bridge or Haswell CPU will get a decent amount of overclocking headroom from even an H75 or H80i, but can hit voltage and thus thermal limits that stem more from how quickly the die can transfer heat to the chip’s heatspreader than how quickly heat can be transferred from the heatspreader to the cooler. Ivy Bridge and Haswell both have very small dies that have a very high heat density, and Intel uses glue and thermal paste instead of solder to bond the heatspreader to the die, substantially reducing the efficiency of heat transfer. Under those circumstances, an H100i or H110 may be able to run its fans at lower speeds, but you’re more apt to hit a heat transfer limit than the limit of the cooling kit itself.

Sandy Bridge-E, Ivy Bridge-E, and just about any modern AMD chip are different stories, though. These chips have lower heat densities, are typically rated for higher wattages, and their dies are soldered to their heatspreaders. Under these circumstances, bigger coolers like the H100i and H110 get a chance to really shine. While Ivy Bridge non-E and Haswell are typically only rated for 77W and 84W respectively, Sandy Bridge-E and Ivy Bridge-E both start at 130W, and AMD’s higher performance chips start at 125W. Overclocking can send these chips north of 200W, at which point the substantial thermal capacity of the H100i and H110 will allow you to hit higher clocks that the majority of air coolers simply won’t be able to reach.

In the midst of all this I haven’t really mentioned the H90, but the H90 can be an excellent alternative to the H80i if your case can support it. You lose the Corsair Link software fan control (which can be very handy and is available on both the H80i and beefier H100i), but the H90, especially when a second fan is added, can be an exceptionally efficient cooler. While our AF140 is designed primarily for use as a case fan, adding one to the H90 can improve performance by as much as eight degrees at the same noise level.

It’s difficult to stress enough how much of an impact the CPU cooler has on the potential performance of your build. While Intel’s mainstream chips can be eventually gated by their own thermal transfer issues, you still want that to be the bottleneck as opposed to the cooler itself preventing your chip from living up to its potential. Likewise, even if you’re not overclocking, a powerful CLC can run its fan or fans at a very low speed and still adequately dissipate the heat from your CPU, and if the cooler is configured to exhaust hot air outside of the case, open up some thermal headroom for the rest of your components. As for overclocking Intel’s enthusiast class and anything in AMD’s very overclocking-friendly lineup, a beefy cooler will let you worry more about whether or not you’re putting too much voltage into your chip instead of being constrained by heat. Either way, it’s hard to go wrong with a high performance CPU cooler, and we most definitely have you covered.